[GHC] #12234: 'deriving Eq' on recursive datatype makes ghc eat a lot of CPU and RAM

[GHC]

#12234: 'deriving Eq' on recursive datatype makes ghc eat a lot of CPU and RAM
-------------------------------------+-------------------------------------
        Reporter:  slyfox            |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:  deriving-perf
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Changes (by RyanGlScott):

 * cc: niteria (added)


Comment:

 Replying to [comment:7 goldfire]:
 > Maybe we should use "stock" for recursive newtypes?

 Maybe. But it bothers me that this used to work fine in 7.10.3. I did some
 git archaeology and discovered that this commit (
 http://git.haskell.org/ghc.git/commit/9cb192ce4b34a472041010df9c30f5d741eb0261
 ) is responsible for this regression, but I don't understand why a change
 to the digraph code led to this.

 niteria, any thoughts as the author of the commit?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12234#comment:8>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler